There is increasing demand in the oil and gas industry for higher performance thermal coatings to insulate and protect off-shore transport conduits operating at high temperatures in water greater than 1,000 meters. In order to maintain the conduit at the required operating temperatures at these depths and to prevent the formation of hydrates and waxes that would compromise pumping efficiency of the fluid in the conduit, the coatings must have low thermal conductivity. Thermal conductivity is decreased through foaming of the coating to some required degree, but the coating must maintain high enough thermal stability and compressive creep resistance to withstand the operating temperatures and hydrostatic pressures acting on the coating in deep water. Without sufficient compressive strength, the insulation will be compressed in thickness, thereby increasing thermal conductivity and altering the dimensions and the thermal and hydrodynamic performance of the system. Also, it is important that the coating remain sufficiently ductile after application on the conduit to prevent cracking during handling and installation, for example during reeling of the conduit onto a lay barge and subsequent deployment therefrom.
Commonly assigned U.S. patent application Ser. No. 11/962,772 to Jackson et al. (published on Jun. 25, 2009 as US 2009/0159146 A1) describes styrenic insulation for application to the outer surface of a fluid and/or gas transport conduit, such as rigid steel pipe. The styrenic insulation layer is adapted to withstand operating temperatures and hydrostatic pressures encountered in water depths of up to about 1,000 meters. The insulation layer may be extruded onto the outer surface of the pipe by use of an annular crosshead die, or may be applied by a side-wrap technique whereby the insulation is extruded through a flat strip or sheet die and then wrapped around a pipe to form an insulation layer on the pipe.
There are also applications where it is desired to apply a layer of thermal insulation to a flexible fluid and/or gas transport conduit, for example as disclosed in U.S. Pat. No. 6,668,866 (Glejbol et al. '866) and U.S. Pat. No. 7,069,955 (Glejbol et al. '955). According to Glejbol et al. '955, one or more thermally insulating layers may be extruded between the inner liner and armour layers of a flexible pipe. According to Glejbol et al. '866, one or more layers of thermally insulating bands may be applied on top of the tensile armour layer, and are shielded from the surroundings by an outer sheath.
However, a need remains for wrappable, pre-formed thermal insulation materials offering superior insulating properties which can be applied to rigid or flexible fluid and/or gas transport conduits such as rigid or flexible oil and gas pipelines, especially for off-shore transport conduits operating at high temperatures in variable water depths up to about 1,000 meters and higher.